There has been a lot of information posted on the subject of linkage adjustment. Thought it might be nice to have it all in one document with photos and diagrams. I have added factory information and what I know on the subject. Feel free to add, or correct as needed.

Sorry if some of these plates have become fuzzy after compression.

The intake venturi is one of the most important aspects of the engine linkage adjustment, engine tuning and automatic transmission shifting. When not adjusted properly problems with improper idle speed, hard automatic transmission shifting, up or down and erratic engine behaviour may result. Proper linkage adjustment will be nearly impossible if the venturi is not correctly set.

The intake venturi stop screw.......

The most common and first item to check is the small slotted stop screw with lock nut on the intake venturi. This is factory set and is frequently mistakenly used as an idle adjustment screw. This stop screw must be set so that the intake linkage arm and venturi valve in the intake closes all the way! When not set correctly too much idle air will be admitted to the engine causing lean idle mixture and/or too high engine idle rpm. An uninformed person may compensate for the situation by tampering with injection and linkage adjustments thus getting the engine even further from being in correct tune.

W113s with automatic transmissions also have a electrical switch attached to the venturi. This switch lowers and raises modulator pressure by activating the three position solenoid on the transmission. Harsh downshifts (especially the last downshift before a stop) may result when not adjusted correctly. Correcting an improper set venturi can make an amazing difference in shifting, engine idle and engine performance.

Disconnect the linkage rod going from the cross over rod to the venturi. If you have a USA version with the vacuum dash pot, you will need to move it out of the way so it does not interfere with the adjustment. The small slotted venturi set screw must be backed off enough to allow the venturi valve to close all the way and then adjusted in just enough to keep the venturi valve from binding in the intake.

USA 280SLs had an "Vacuum throttle control" on the intake venturi linkage. A special linkage with a "slip joint" was also used between the venturi and the cross-over rod on the engine. Adjust the slip joint linkage so it is fully compressed with the engine running and warm at idle in neutral. Adjust the vacuum control/linkage to zero clearance. Now with the transmission in gear, the throttle lever will open 1.0 mm to 1.5 mm.If you have a factory shop manual with the USA versions look on page 07-14/7. It gives the procedure to adjust the unit. Adjustments of the other linkage and tune-up items can follow afterwards if the idle is too high or too low or the mixture is incorrect.

During regular maintenance engine linkages should be lubricated with a light oil. Often times the block pivot is missed and may begin to bind or seize after periods of inactivity or storage. Try using some penetrant first then oil after it becomes free. This photo is a sedan pivot. The location is the same (under the intake manifold) and the unit is very similar. Also not the factory coolant drain plug location in the picture.

Here is some information on the firewall accelerator pedal linkage and adjustment. The linkage between the block pivot and the intake manifold lever should be checked first before tampering with the firewall adjustment.

When the accelerator pedal is at the floor the venturi valve should be wide open. If not you are loosing a lot of power. This is fairly common problem. With automatics the pedal must also contact the "kick down switch". Adjust at the firewall after checking the other linkages.

Information and diagram contributed by "merrill" Matt Merrill;

"I have put the part numbers for another linkage bushing, ball stud , washer and nut. all are available at the price in the photo. the bushings are only in germany"..........

Joe,I thought I saw a post that discussed linkage adjustment that went something like this.

"set the venturi linkage to 233 mm in length from the centers of the ball socket, then make sure that when the inj pump is wide open the intake venturi is wide open."

1. is the venturi linkage referring to the ijn pump to cross link or the cross link to the intake venturi? the linkage for the inj pump to cross linkage on my car was exactly 233 mm center to center.I just want to make sure this is ok.

(the link from the cross linkage to the intake was about 12 inches long. while the inj pump to cross linkage was about 9 1/2 inches long.)

2. when the inj pump was wide open, the intake venturi was not wide open, so I lengthened the linkage from the cross linkage to the intake venturi. I also made sure that the butterfly valve in the intake fully closed / opened after adjustment.

It will be interesting to see if this changes the performance of the car.

I am glad you caught this! Now I need to go back and correct this, yes the 233mm dimension is for the linkage rod going from the injection pump to the cross over rod!

Be careful, Yes make sure that the venturi is closed and the injection pump lever is on its stop. Also make sure the venturi stop screw is only adjusted just enough to keep the butterfly valve from binding.

Make sure that the engine is getting full throttle when the accelerator is on the floor. There is a accelerator pedal height adjustment at the fire wall near the brake booster. By loosening the 13mm bolt head and removing the spring, you will be able to adjust the accelerator pedal height. Afterward make sure the accelerator pedal gives you full throttle when floored. Also make sure that the accelerator pedal just hits the kick down switch (on automatics) when the pedal is depressed at full throttle. Changing the length of the linkage rod going to the block pivot will also change pedal travel and throttle.Thanks,

I have never seen a specific length listed for the rod between the pivot and the manifold, but if it is too short your accelerator pedal may be too high. If it is too long you may not be getting full throttle. One easy test is to hold the accelerator pedal all the way to the floor (engine off). Next have someone check to see if the venturi is open all the way.

if you can mail me the pictures in as large a format as available, I can make this into a document which I can create a "member-only" downloadable PDF of. This pdf then should print great on someone's printer, and will have full picture quality.

Let me know if you think this would be a good idea, and you can mail me the original images to admin@sl113.orgPeter

Hello Waqas,The linkage rod between the injection pump and cross over rod should be the same on the 250 and 280 series in both the SL and sedans. I am fairly certain that the 230SL is also the same. There may be some differences in the other linkages depending on the model. As far as I know the installed lengths of the other rods is not called out in the BBB, just the one from the pump to the cross over rod 233mm.

Installing the 233 mm rod and setting up the venturi to be completely closed will dictate the length of the rod going from the venturi to the cross over rod. Also use the alignment bore in the linkage support if your car has it. The linkage rod going to the block pivot should be set so the venturi is all the way open when the accelerator is at the floor while still allowing the venturi to completely closed when the pedal is up.

Thanks for the great information! I have a quick question about the Progressive Regulating Linkage (top diagram in your linkage 13.JPG pic):

Is there supposed to be some play in the linkage when I press the accelerator? I have the linkage rod adjusted so the roller rests as indicated, however, I have to depress the pedal about a 1/2" or so before the linkage engages (i.e., the linkage engages the roller); is this the correct configuration? I hope that isn't too vague or misleading?

Thanks,Steve

Steve IatrouSeaside, CA1964 230sl roadsterWhite (050)/Black (116)

Logged

Steve Seaside, CA

RCS Coupe

Installing the 233 mm rod and setting up the venturi to be completely closed will dictate the length of the rod going from the venturi to the cross over rod. Also use the alignment bore in the linkage support if your car has it. The linkage rod going to the block pivot should be set so the venturi is all the way open when the accelerator is at the floor while still allowing the venturi to completely closed when the pedal is up.

Joe Alexander

Sorry, but I need to beat this out one more time. I am installing all new (or replated) link rods, balls, sockets, and pivots from the pedal to the venturi and FI pump. Mine is an M129 (250SL) engine, non-US spec, manual transmission, R11 FI pump.With a pile of shiny metal bits in front of me, some rods right threaded, others left-threaded, I have to start somewhere to get it all back together and working.

For the link rod between the FI pump and the crossover shaft: is the length dictated by the cross shaft being on the alignment bore in the shaft support and the FI pump lever on the stop, or does the link need to be 233 mm long?

With my FI pump lever on the stop and the cross shaft aligned through the support hole, the link rod measures 230 mm center-to-center (socket balls). Lengthing the rod to 233 mm will open the FI pump off the stop with the throttle valve shut. Any thoughts on this?

quote:With my FI pump lever on the stop and the cross shaft aligned through the support hole, the link rod measures 230 mm center-to-center (socket balls). Lengthing the rod to 233 mm will open the FI pump off the stop with the throttle valve shut. Any thoughts on this?

Sounds like some of the other linkage rod lengths have been changed. Set the injection pump rod to 233mm, disconnect the other rods, including the rod going to the block pivot. Adjust and install the linkage from the cross over rod to intake venturi (venturi must be closed) now install the block pivot rod so it does not disturb the linkage at rest. Next make sure that the venturi is fully open when the accelerator is on the floor. When the accelerator pedal is at rest the venturi should be completely closed and on the linkage lever on the stop at the injection pump.

By the looks of the diagram it appears that the progressive linkage is meant to move a bit before things start to happen, however the "roller openings" do wear and yours may be bit excessive. In this case you may wish to replace the linkage plate or adjust it a bit off the rest to compensate. Make sure you get "full throttle" (venturi fully open) with the accelerator pedal on the floor.